<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

    <script>
        'use strict'
        function people()
        {
            console.log(this);  //window  没有new  ，严格模式下为undefined
        }
        people()

        var age=10;
        delete age;
        console.log('删除之后age==>',age);


    </script>
    
</body>
</html>